The present invention relates to a video signal recording and reproducing apparatus that compresses video signals having different formats with a high efficiency, and records as well as reproduces the compressed video signals.
Recently, several new broadcasting systems, such as HDTV (high definition television), ATV (advanced television), etc. have been developed in the engineering field of broadcasting industry, and some of the new systems are now in operation.
On the other hand, various systems are proposed to be the next generation broadcasting system, e.g., a progressive signal method, in other words, a 480p signal method, which is converted from the interlace signal method of NTSC system where 525 scanning lines are employed. Meanwhile, the 480p signal method handles 525 scanning lines in the progressive method; however, a number of active lines are 480, thus the system is named for this number. The conventional interlace system is called xe2x80x9c480ixe2x80x9d in order to distinguish from the progressive method. The 480p signal method is now prescribed as the DTV (digital television) standard of the U.S.
The 480p signal of progressive signal method is described hereinafter.
FIG. 16 is a schematic diagram depicting signal modes of interlace and progressive method. By the interlace mode, 30 frames of picture data are produced per second, one picture data (one frame) is scanned with every other scanning line of 525 lines, thus 60 picture data (field) per second, each frame scanned with 262.5 lines, are transmitted. A digital studio standard employing the interlace mode is prescribed in Recommendation ITU-R.601-3, of which sampling frequency is, luminance signal: 13.5 MHz, color difference signal: 6.75 MHz. This xe2x80x9c4:2:2 signalxe2x80x9d is referred to xe2x80x9c4:2:2-i signalxe2x80x9d hereinafter to identify that this signal is in the interlace mode.
The progressive method, on the other hand, produces 60 picture data (frame) per second, and one picture data is scanned by 525 scanning lines (including 480 active lines) without interlacing. The progressive signal, of which picture is formed with 525 scanning lines, is digitized by a xe2x80x9c8:4:4 signalxe2x80x9d format, i.e., doubled sampling frequency of the digital studio standard in the interlace mode. The sampling frequency of the progressive signal is thus, luminance signal: 27 MHz, color difference signal: 13.5 MHz., which is twice as much as that of the xe2x80x9c4:2:2 signalxe2x80x9d. The xe2x80x9c8:4:4 signalxe2x80x9d is now studied to divide into a main signal and a sub-signal for transmitting, i.e., the main signal comprising one luminance signal and two color difference signals, and the sub-signal comprising also one luminance signal and two color difference signal so that the sub-signal interpolates the main signal. The xe2x80x9c8:4:4 signalxe2x80x9d is thus divided into the main and sub signals which are assigned to every other scanning line respectively. The main signal and sub signal of this method are an independent interlace signal having 525 scanning lines per frame, and are the same as the xe2x80x9c4:2:2 signalxe2x80x9d. The coupled main signal and sub signal is hereinafter referred to xe2x80x9c4:2:2:4:2:2 signalxe2x80x9d or xe2x80x9c4:2:2p signalxe2x80x9d.
FIG. 18 depicts a sampling structure of the xe2x80x9c4:2:2p signalxe2x80x9d on a screen. As shown in FIG. 18, a video signal is divided into the main signal and sub signal in both an even frame and an odd frame. The main signals and sub signals are alternately arranged on vertical and horizontal lines in temporal-spatial wise.
When the xe2x80x9c8:4:4 signalxe2x80x9d or xe2x80x9c4:2:2p signalxe2x80x9d is transmitted, the color difference signal of xe2x80x9c8:4:4 signalxe2x80x9d undergoes, e.g., a vertical filter as shown in FIG. 17 in vertical direction in order to limit its bandwidth before transmitting the color difference signal in each line, for the color difference signal carries less information than the luminance signal does, therefore the human visual property does not sense deterioration of the color difference signal. In FIG. 17, the filter comprises 1H delay line 120, 121 delaying a signal for one horizontal scanning period, a multiplier 122, 124 and an adder 123. The numbers printed in the boxes representing the multipliers 122 and 124 in FIG. 17 are coefficients of multiplication. The color difference signal is limited in its band by e.g., the vertical filter as shown in FIG. 17, then the signals are decimated in each line, then the color difference signal only on the main signal side are transmitted, while that on the sub signal side is not transmitted.
The above transmitted signal is called xe2x80x9c4:2:2:4:0:0 signalxe2x80x9d or xe2x80x9c4:2:0pxe2x80x9d signal because the sub signal does not carry the color difference signal. The xe2x80x9c4:2:0p signalxe2x80x9d is prescribed as SMPTE294M standard. When the progressive signal is converted into the xe2x80x9c4:2:0p signalxe2x80x9d in transmission, recording or playing back, the transmission band can be effectively reduced without deteriorating a visual quality of the video signal.
On the other hand, the color difference signal decimated on the sub-signal side can be reproduced by providing the main signal with an interpolation filter as shown in FIG. 19 or 20. FIG. 20 shows the easiest way for the reproduction. In FIG. 19, the filter comprises 1H delay lines 130, 131 and 132 delaying a signal for one horizontal scanning period respectively, multipliers 133, 134, 135, 136 and 138, and an adder 137. The numbers printed in the boxes representing the multipliers are coefficients of multiplication. In FIG. 20, the filter comprises 1H delay line 140 active in one horizontal scanning period, an adder 141 and a multiplier 142. The number printed in the box 142 representing the multiplier is a coefficient of multiplication. Since the color difference signal on the sub-signal side can be reproduced by the filter shown in FIG. 19 or 20, the xe2x80x9c4:2:0p signalxe2x80x9d can be converted into the xe2x80x9c4:2:2p signalxe2x80x9d, further, the xe2x80x9c4:2:2p signalxe2x80x9d can be converted with ease into the xe2x80x9c4:2:2-i signalxe2x80x9d by adding the main and sub signals and dividing 2 into the addition result, as FIG. 21 shows an example. In FIG. 21, a filter comprises an adder 150 and a multiplier 151. The number printed in the box of multiplier 151 is a coefficient of multiplication.
Besides the xe2x80x9c480p signalxe2x80x9d method, various methods are proposed in HDTV (high definition television) system and other systems aiming for the higher resolution than that of the present system. For instance, 1125i/1035i (1125 scanning lines including 1035 active lines), 1125i/1080i method in the interlace system, and 750p/720p (750 scanning lines including 720 active lines) in the progressive signal method of HDTV system are proposed.
Various proposals of TV systems accompany the developing of hardware corresponding to the systems such as acquisition devices, equipment for studios. The next generation broadcasting system; however, has just undergone a test operation, therefore, materials produced by the acquisition devices are converted into the present television system to be on-air. For instance, a program is produced by HDTV cameras and VCRs, and the program is on-air through the satellite broadcasting as HDTV, and also the program is converted into the present television system and on-air through the terrestrial broadcasting.
It sometimes happens that a program is produced using devices and equipment corresponding to various broadcasting methods, e.g., a program is produced by combined hardware including devices for high resolution television such as HDTV, 480p and other devices for the present television system, and the program thus produced is on-air through the present broadcasting system.
In such a case, the program must be undergone the process shown in FIG. 15 before on-air.
The conventional method shown in FIG. 15 is now detailed.
In FIG. 15, a first VCR 100 is used in xe2x80x9c480i signalxe2x80x9d system of interlace mode, and reproduces the xe2x80x9c4:2:2-i signalxe2x80x9d where a sampling frequency ratio of luminance signal vs. color difference signals is 4:2:2. A second VCR 101 is used in xe2x80x9c480p signalxe2x80x9d system of progressive signal, and reproduces xe2x80x9c4:2:0p signalxe2x80x9d. A third VCR 102 reproduces HD signals containing e.g., 1125 scanning lines which includes 1080 effective lines. A fourth VCR 106 records and reproduces video signals formatted in xe2x80x9c4:2:2-i signalxe2x80x9d of the present television system. All the VCRs handle compressed video signals.
The first VCR 100 reproduces and outputs xe2x80x9c4:2:2 signal 107xe2x80x9d. The second VCR 101 reproduces xe2x80x9c4:2:0p signalxe2x80x9d, which undergoes a scanning line converter 103 which is formed by a simple filter as shown in FIG. 21, and produces xe2x80x9c4:2:2-i signal 110xe2x80x9d. The third VCR 102 reproduces a HD signal 109, which undergoes a format converter 104 to be converted into xe2x80x9c4:2:2-i signalxe2x80x9d. The format converter 104, in this case, is called a xe2x80x9cdown converterxe2x80x9d, and has filters both in vertical and horizontal directions on the screen. The format converter 104 converts a number of scanning lines and samples per line to produce xe2x80x9c4:2:2-i signal 111xe2x80x9d. A switcher 105 selects one of input signals 107, 110 and 111 of xe2x80x9c4:2:2-ixe2x80x9d system, and outputs the selected signal as an output signal 112 to the fourth VCR 106, which edits signals including the selected signal on its tape to produce a program.
In FIG. 15, if additional device of another system is used, the corresponding VCR as well as converter must be prepared, and signals are edited on the tape.
In the above conventional process, e.g., when a picture of xe2x80x9c4:2:2-i signalxe2x80x9d is produced by combining a picture of xe2x80x9c4:2:0p signalxe2x80x9d and a picture of xe2x80x9c4:2:2-i signalxe2x80x9d, the xe2x80x9c4:2:0p signalxe2x80x9d is firstly converted into the xe2x80x9c4:2:2-i signalxe2x80x9d, then secondly compressed again for being edited on the tape. The repeating signal compression and decompression results in deteriorating a picture quality. Further, necessary times for decoding, line conversion and format conversion differ depending on formats of original picture as well as converted picture, it is thus impossible to record the signals in the fourth VCR on real time base. There are still other problems as follows in addition to the above problems:
1. Three VCRs in total are necessary, i.e., one for reproducing the xe2x80x9c4:2:0p signalxe2x80x9d, one for reproducing the xe2x80x9c4:2:2-i signalxe2x80x9d and the other for recording the xe2x80x9c4:2:2-i signalxe2x80x9d. Further a line converter for converting the xe2x80x9c4:2:0p signalxe2x80x9d into the xe2x80x9c4:2:2-i signalxe2x80x9d is required. These devices require much of labor and cost.
2. Editing process, such as insertion and assembly, does not allow any seams in a chain of signals and yet consumes a large number of times.
The present invention aims to address the above problems and provide a recording and reproducing apparatus which can record and reproduce video signals of different numbers of scanning lines and resolutions with no seams between video signals and without deteriorating picture quality.
In order to achieve the above goals, the present invention compresses a various of video signals, which have different numbers of scanning lines and resolutions, into signals having different bit-rates lower than the maximum bit-rate so that a recording and reproducing apparatus can process. The video signals can be thus continuously recorded and reproduced.
According to the first invention, a video signal recording apparatus comprises the following elements:
(a) compressing means which receives at least two kinds of video format signals, recognizes the formats and compress the signals instantly responding to respective information quantity of the video signals,
(b) recording means which records (1) the compressed signals and (2) format recognition signals for recognizing a format of the compressed signals without seams, on at least one helical track formed on a magnetic tape.
According to the second invention, a video signal recording apparatus comprises the following element:
Recording means which receives two or more different kinds of compressed video signals, and records (1) the compressed signals and (2) format recognition signals for recognizing a format of the compressed signals with no seams, on at least one helical track formed on a magnetic tape.
According to the third invention, a video signal reproducing apparatus comprises the following elements:
(a) reproduction means for reproducing signals from the magnetic tape in which the compressed video signals in different formats are recorded without seams on at least one track,
(b) decompressing means for (1) recognizing formats of the reproduced signals using the format recognition signals tapped off from the reproduction means, (2) changing a decompression rate instantly responding to the format recognized, and (3) decompressing the reproduced signals into respective original formats with no seams, and
(c) conversion means for converting the decoded video signals into another format.
The recording means and reproducing means of the present invention can thus realize to record and reproduce video signals continuously regardless of the formats of the video signals. As a result, video signals having respective numbers of scanning lines and resolutions can be recorded seamlessly on an identical magnetic tape. When producing a program with different video signals having respective numbers of scanning lines and resolutions, production staff are not requested to prepare VCRs for reproduction, conversion means of scanning lines or format, and VCRs for recording, i.e., all of the devices corresponding to respective video signals, therefore, the present invention can significantly save time and labor for producing a program, further the present invention can prevent the picture quality from degrading due to repetitive conversions of scanning lines as well as repetitive signal compression.
The present invention also ensures that no disturbance or no seam is observed when a magnetic tape containing the different video signals having respective numbers of scanning lines and resolutions is played back.